Vowel Synthesis
From PiWiki
Jonas Beskow
https://www.youtube.com/watch?v=xv4PlpUTf_c
http://www.speech.kth.se/~beskow/papers/fon98veiron.pdf
http://www.speech.kth.se/wavesurfer/formant/ <-- can't get this working on OSX because of TCL problems
^ source code has 4 formant frequencies for many vowels (>20)
STRAIGHT
Uses Matlab
praat
http://www.fon.hum.uva.nl/praat/manual/Source-filter_synthesis.html
Csound
https://en.wikipedia.org/wiki/Csound
WORLD
http://ml.cs.yamanashi.ac.jp/world/english/
MISC
https://ccrma.stanford.edu/~jos/fp/Formant_Filtering_Example.html